Biology subjects

Torben Heick Jensen

Publications and source records attributed to Torben Heick Jensen.

3 recordsLinked to original sources

bioRxiv2016

Principles for RNA metabolism and alternative transcription initiation within closely spaced promoters

Mammalian transcriptomes are complex and formed by extensive promoter activity. In addition, gene promoters are largely divergent and initiate transcription of reverse-oriented promoter upstream transcripts (PROMPTs). Although PROMPTs are commonly terminated early, influenced by polyadenylation sites, promoters often cluster so that the divergent activity of one might impact another. Here, we find that the distance between promoters strongly correlates with the expression, stability and length of their associated PROMPTs. Adjacent promoters driving divergent mRNA transcription support PROMPT formation, but due to polyadenylation site constraints, these transcripts tend to spread into the neighboring mRNA on the same strand. This mechanism to derive new alternative mRNA transcription start sites (TSSs) is also evident at closely spaced promoters supporting convergent mRNA transcription. We suggest that basic building blocks of divergently transcribed core promoter pairs, in combination with the wealth of TSSs in mammalian genomes, provides a framework with which evolution shapes transcriptomes.

Genomics↗

bioRxiv2014

Skip and bin: pervasive alternative splicing triggers degradation by nuclear RNA surveillance in fission yeast

Exon-skipping is considered a principal mechanism by which eukaryotic cells expand their transcriptome and proteome repertoires, creating different slice varaiants with distinct cellular functions. Here we analyze RNA-seq data from 116 transcriptomes in fission yeast (Schizosaccharomyces pombe), covering multiple physiological conditions as well as transcriptional and RNA processing mutants. We applied brute-force algorithms to detect all possible exon-skipping events, which were ubiquitous but rare compared to canonical splicing events. Exon-skipping events increased in cells deficient for the nuclear exosome or the 5-3 exonuclease Dhp1, and also at late stages of meiotic differentiation when nuclear-exosome transcripts were down-regulated. The pervasive exon-skipping transcripts were stochastic, did not increase in specific physiological conditions, and were mostly present at below 1 copy per cell, even in the absence of nuclear RNA surveillance and late during meiosis. These exon-skipping transcripts are therefore unlikely to be functional and may reflect splicing errors that are actively removed by nuclear RNA surveillance. The average splicing error-rate was [~]0.24% in wild-type and [~]1.75% in nuclear exonuclease mutants. Using an exhaustive search algorithm, we also uncovered thousands of previously unknown splice sites, indicating pervasive splicing, yet most of these novel splicing events were rare and targeted for nuclear degradation. Analysis of human transcriptomes revealed similar, albeit much weaker trends for pervasive exon-skipping transcripts, some of which being degraded by the nuclear exosome. This study highlights widespread, but low frequency alternative splicing which is targeted by nuclear RNA surveillance.

Genomics↗

bioRxiv2014

Nuclear stability and transcriptional directionality separate functionally distinct RNA species

Mammalian genomes are pervasively transcribed, yielding a complex transcriptome with high variability in composition and cellular abundance. While recent efforts have identified thousands of new long non-coding (lnc) RNAs and demonstrated a complex transcriptional repertoire produced by protein-coding (pc) genes, limited progress has been made in distinguishing functional RNA from spurious transcription events. This is partly due to present RNA classification, which is typically based on technical rather than biochemical criteria. Here we devise a strategy to systematically categorize human RNAs by their sensitivity to the ribonucleolytic RNA exosome complex and by the nature of their transcription initiation. These measures are surprisingly effective at correctly classifying annotated transcripts, including lncRNAs of known function. The approach also identifies uncharacterized stable lncRNAs, hidden among a vast majority of unstable transcripts. The predictive power of the approach promises to streamline the functional analysis of known and novel RNAs.

Genomics↗